Identification of a fault

ABSTRACT

An apparatus, method, and system are provided for determining a location of an error source. Equalization coefficients may be retrieved and an average period of time between localized peak amplitudes may be determined. The average period of time may be multiplied by a velocity of propagation associated with a communication channel to determine an approximate location of the error source. The equalization coefficients may correspond to the inverse of the frequency response associated with the communication channel and may be updated over time using replacement or combination (e.g., convolution) techniques.

RELATED APPLICATIONS

The present application is related to, incorporates by reference, andclaims the priority benefit of U.S. Provisional Patent Application No.61/301,835, entitled “Modem Signal Usage and Fault Isolation”, filedFeb. 5, 2010.

FIELD OF ART

The features described herein generally relate to providing users withaccess to content over a network. More specifically, aspects of thedisclosure describe identifying a likely or approximate location of apotential problem or error associated with a network.

BACKGROUND

From the perspective of a service provider or network operator, the mostcommon driver for user initiated contact related to service problems istypically caused by in-home wiring issues. For example, standard metricsused to evaluate user terminal (e.g., modem) performance are subject toequalization and may provide a misleading or incomplete picture ofsignal performance. Standard metrics generally provide a goodrepresentation of the user's overall experience, but the equalizationcan mask signal impairments which may manifest intermittently and notnecessarily at the time of analysis.

Furthermore, intermittent issues are often hidden by equalizationemployed by user terminals. Intermittent transmission problems oftenresult in inconclusive troubleshooting and a poor user experience. Thisoften leads to a user repeatedly contacting the network operator tocomplain about issues such as failures and difficulties on the part of atechnician in recreating an error condition. When debugging a fault,traditional performance metrics are generalized and fail to provide anindication as to where the source of the fault is located.

Improved techniques are needed to minimize operational down-time,shorten service time, and enhance a user's experience.

SUMMARY

This summary is not intended to identify critical or essential featuresof the disclosure provided herein, but instead merely summarizes certainfeatures and variations thereof.

In some embodiments, distortion compensation (pre-equalization) may beperformed at a user terminal prior to transmission of a signal from theuser terminal In some embodiments, distortion compensation(post-equalization) may be performed after the signal has beentransmitted from the user terminal and received at a receiving device.The distortion compensation techniques may be used to correct fordeficiencies or non-idealities in a network (e.g., the components orcommunication channel(s) thereof). For example, the distortiontechniques may be used to minimize or eliminate demodulation errors atthe receiving device, thereby promoting accuracy in terms of symbolrecognition/detection.

In some embodiments, adaptive (or dynamic) equalization coefficients maybe gathered from one or more devices (e.g., a user terminal, a modem, atermination system such as a cable modem termination system (CMTS),etc.). The equalization coefficients may include both time and frequencyrelated information. Analysis of the equalization coefficients in termsof magnitudes and/or location relative to a reference or main-tap mayprovide a ratio that can be used to discriminate impairments that aretypically near the user terminal versus those which are beyond a user'slocation (e.g., a user's home). For example, given a data symbol period,the source of an error located a distance from the user's terminal maybe approximated using velocity of propagation mathematics. The distancemay correspond to a measurement between two impedance mismatches(reflectors) which have formed a signal cavity, causing a recursiveecho. In most cases of large reflections on a plant, one of thereflectors is co-located within a user's premises. That said, thedistance is not actually from the user's terminal (e.g., a modem),rather the user's premises (e.g., the user's home).

The equalization coefficients may be indicative of samples of a signaltaken at discrete periods of time. Each sample may coincide with a tapof a tap-delay filter. For example, the main-tap may coincide with asignal from a user terminal at a discrete instant in time and the othertaps may represent prior or future samples of the signal relative to themain-tap. In some embodiments, one or more processors associated withone or more devices may execute instructions stored in a memory toimplement the tap-delay filter, to establish equalization coefficients,and to analyze the equalization coefficients.

Other details and features will also be described in the sections thatfollow.

BRIEF DESCRIPTION OF THE DRAWINGS

Features will become apparent upon a review of this disclosure in itsentirety, including the drawing figures provided herewith, the contentsof which are fully incorporated herein by way of reference.

Some features herein are illustrated by way of example, and not by wayof limitation, in the figures of the accompanying drawings and in whichlike reference numerals refer to similar elements.

FIG. 1 illustrates an example information distribution system.

FIG. 2 illustrates an example architecture, with a closer level ofdetail on one of the premises illustrated in the FIG. 1 network.

FIG. 3 illustrates a constellation pattern associated with a modulationtechnique described herein.

FIGS. 4 and 5A-5B illustrate tap bar graphs suitable for demonstratingone or more aspects of this disclosure.

FIG. 6 illustrates a method suitable for practicing one or more aspectsof this disclosure.

DETAILED DESCRIPTION

It is noted that various connections between elements are discussed inthe following description. It is noted that these connections aregeneral and, unless specified otherwise, may be, for example, wired orwireless, direct or indirect, and that this specification is notintended to be limiting in this respect.

FIG. 1 illustrates an example information distribution network 100 onwhich many of the various features described herein may be implemented.Network 100 may be any type of information or content distributionnetwork, such as satellite, optical fiber, coaxial cable, telephone,cellular, wireless, etc. The network may be a hybrid fiber/coaxdistribution network found in many television networks. Such networks100 may use a series of interconnected lines 101 to connect multiplehomes 102 to a provider's headend or central location 103. The centrallocation 103 may transmit downstream information signals onto the lines101, and each home 102 may have a tuner used to receive and processthose signals. Signals may also include upstream transmissions fromhomes 102 to central location 103.

The lines 101 may be a series of interconnected lines of different type,such as optical fiber and/or coaxial cables. There may be one lineoriginating from the central location 103, and it may be split a numberof times to distribute the signal to various remote sites such as homes102 in the vicinity (which may be many miles) of the central location103. The lines 101 may include components not illustrated, such assplitters, filters, amplifiers, etc. to help convey the signal clearly.Portions of the lines 101 may also be implemented with fiber-opticcable, resulting in a hybrid fiber/cable (HFC) network of lines 101. Byrunning fiber optic cable along those portions, signal degradation inthose portions may be significantly minimized, allowing a single centrallocation 103 to reach even farther with its network of lines 101 thanbefore. Portions of lines 101 may also be implemented via wirelesslinks.

FIG. 2 illustrates a closer view of one of the remote sites, home 102from FIG. 1. As illustrated, the home 102 may be connected to thenetwork 100 by, for example, a wireless link, optical fiber or coaxialcable feed 201. The feed may be connected to a gateway device 202, whichmay serve as an interface between the devices within the home 102, andthe external devices out on the network 100. The gateway itself mayinclude tuners, modulators, demodulators, etc. to communicate out on thenetwork 100, and may also include interface components to communicatewith the devices in the home.

As for the network in the home, the specific types of components mayvary, depending on the type of communication network used in the home.One example may be an Internet Protocol network 203 carried over thehome's internal coaxial wiring under the MoCA (Multimedia Over CoaxAlliance) standard. To this end, the gateway 202 may be an IP transportgateway, using IP communications to communicate with the devices in thehome, and with devices outside the home (e.g., via a DOCSIS CMTS in aHFC-type network, for example). Other networks, such as wirelessnetworks, may alternatively be used.

Various devices may communicate on the network in the home. For example,one or more personal computers 204 may use the gateway 202 tocommunicate with other devices on the provider's network, such as aprivate or public network (e.g., the Internet). Customer premisesequipment (CPE) 205, such as set-top boxes (STBs), may receive IPdistribution of video content received at the gateway 202, and convertthat video content into a format suitable for display on correspondingdisplay devices 206, such as televisions, monitors, handheld devices,etc. Alternatively, display devices 206 may incorporate functionality ofpremises equipment 205. For example, the CPE 205 may receive an MPEG2stream of video, and may process that stream to generate an HDMI (HighDefinition Multimedia Interface) output signal to each CPE 205 orcorresponding display device 206. While STBs are described below, oneskilled in the art would appreciate that devices in addition to, or inlieu of STBs, such as personal computers (PCs), servers, gateways, etc.,may be used in some embodiments.

Some display devices in the home, however, might not have their own CPE,such as a STB. Or they might not have the circuitry needed to decode theMPEG2 stream of video received at the gateway 202. For example, displaydevices such as televisions 207 a and 207 b might be old-fashionedanalog televisions, having tuners configured to tune to the analogbroadcast channels defined by the NTSC (National Television SystemCommittee). Or, they may be digital televisions not equipped to receiveand decode the latest form of digital compression or modulation used onthe network 100. To support such legacy devices, the gateway 202 mayinclude a local wireless transmitter 208.

The local wireless transmitter 208 may be configured to transmit alow-power radio frequency channel carrying video signals of a selectedprogram for local reception within the home. For example, if thetelevision 207 a is an analog television, the gateway 202 may use thetransmitter 208 to transmit a selected program as an NTSC video signalon an NTSC Channel (e.g., channel 2). That channel and signal can betuned by the television 207 a, and displayed for the user's consumption.In this manner, legacy devices may continue to be used even iftransmission techniques advance. The transmitter 208 may use any desiredwireless format, such as IEEE 802.11, ZIGBEE, BLUETOOTH, etc. An 802.11transmitter 208 may be especially useful, since the 2.4 GHz range ofthat standard happens to overlap the 300 MHz-3 GHz frequency range ofthe NTSC UHF channels.

Any number and type of devices (e.g., computers, mobile devices, cablemodems, telephones, set top boxes, etc.) may be located within thenetwork of FIGS. 1 and 2. Those devices located at a user's premises,such as home 102, may generally be referred to as user terminals.

By way of introduction, equalization may be performed to account fornon-idealities in the frequency response associated with transmissionsfrom a user terminal to another device (e.g., a termination system (TS))by way of a communication channel. The frequency response may be used todemonstrate a difference between what is transmitted by the userterminal and what is received by the device. This difference may becaused by and may sometimes be referred to as distortion. Equalizers maybe used to perform the equalization and may be configured to dynamically(e.g., adaptively) correct for the difference. In some embodiments, theequalizer may be implemented using one or more (digital signal)processors in conjunction with one or more algorithms embodied asinstructions stored in a memory. The equalization may correspond to theinverse of the frequency response associated with the network, (e.g.,the communication channel and the components making up the network),such that when a signal is received from the user terminal at thedevice, the signal appears undistorted to the device.

In conducting equalization, errors such as symbol errors followingdemodulation at a receiver may be eliminated or reduced. For example, acontext involving a grid mapping of 64-quadrature amplitude modulation(64-QAM) is shown in FIG. 3. Each symbol of the 64-QAM grid may berepresented by a box, one of which is shown as box 302 in FIG. 3. Box302 may define a decision region, where a received symbol may be decodedas a corresponding given symbol when it is located inside box 302.

In an ideal operating environment, every received symbol may be locatedat the exact center of each box. Due to non-ideal effects, however, ascatter in the received symbols may result in actual implementations.Circle 308 may represent a scatter of symbols with respect to box 302,where the radius of circle 308 may represent where the vast majority ofthe symbols corresponding to box 302 are decoded. The radius of circle308 may also represent a tolerance (such as a quality of service (QoS)parameter) that a network operator or service provider needs to satisfy.For example, the distance from circle 308 to box 302 may represent anoise margin in some embodiments.

Dot 314 may represent an instance where a symbol is received that fallsoutside of a circle. As the location of dot 314 moves further from thecenter of a box (and closer to the perimeter of that box), a greaterlikelihood may exist that the symbol will not be received properly(e.g., that the received symbol will be decoded incorrectly at areceiver).

Equalization may have a tendency to more closely focus the distributionof the received symbols towards the center of each of the sixty-fourboxes making up the grid, thereby improving the relative noise marginswith respect to each of the decision boundaries. The grid on the left ofFIG. 3 shows a scatter of data that is well within the decisionboundaries (e.g., the perimeters of each box), whereas the grid on theright of FIG. 3 shows the scatter of data approaching and intersectingthe perimeters of each box, and thus, likely leading to symboldemodulation errors. While QAM modulation is shown in FIG. 3, in someembodiments different transmission or modulation techniques may be used.For example, amplitude modulation (AM), frequency modulation (FM), andthe like may be used.

One type of analysis of network performance may be based on apost-equalization perspective. This type of analysis may provide insightinto a user's experience, but such an analysis may hide intermittent orlatent problems by obscuring plant issues until a problem becomesvisible from the user's perspective. Higher quality service may beprovided to a user by diagnosing problems/issues in advance of when theyactually manifest themselves at the user's location.

In general, equalizer coefficients may be complex numbers (e.g., havereal and imaginary components) and may include time and frequencyinformation. The equalizer coefficients may be represented in a bargraph format, similar to the bar graph shown in FIG. 4. In the bar graphof FIG. 4, twenty-four (24) coefficients are shown. The twenty-fourcoefficients may represent time-delayed samples (by way of a tap-delayfilter) of a signal transmitted from a user terminal to another device(e.g., a TS). In some embodiments, a different number of coefficients(and a corresponding different order tap-delay filter) may be used.

A reference or main-tap may be designated to correspond to a particulartime period of analysis. For example, in an example system employingDOCSIS 2.0, the main-tap is in the eighth position. Under DOCSIS 1.1.,the main-tap is in the fourth position. Different tap positions may bedesignated as the main-tap in some embodiments. For purposes ofillustration, assuming that the main-tap corresponds to the eighthposition in FIG. 4, those taps to the right of the main-tap (e.g., tappositions 9-24 in FIG. 4) may represent past samples relative to thetime associated with the main-tap, and those taps to the left of themain-tap (e.g., tap positions 1-7 in FIG. 4) may represent futuresamples relative to the time associated with the main-tap.

The equalizer coefficients may indicate how hard the user terminal isworking to redistribute energy across the span of equalization based onthe error or distortion source. In an ideal network operatingenvironment, all the energy of the transmitted signal would beconcentrated in the main-tap. However, due to distortion sources ornon-idealities typically present in actual operating environments,energy is located in taps other than the main-tap.

The types of distortion that may be present may include linear andnon-linear distortions. Linear distortions may be those distortions thatimpact the amplitude and/or phase of an original signal.Micro-reflections (which, as seen by a receiver, may be a copy of atransmitted signal arriving late and with a reduced amplitude),amplitude distortion (which may represent undesirable variation in acommunication channel's amplitude response and may result in distortionof a signal's amplitude), and group delay variation (which may representundesirable variation in a communication channel's phase response andmay result in distortion of a signal's phase or a variation in thepropagation of frequency components of the signal across the channel)are examples of linear distortions. Non-linear distortions may be thosedistortions that generate distortion components, including harmonics ofthe original signal or multiples of the original signal with otherenergy present in a return band. The equalizer coefficients may provideinsight into the actual operating environmental conditions.

A user terminal may engage in a series of communications with anotherdevice (e.g., a TS) for purposes of establishing the values of theequalization coefficients. For example, the user terminal may transmit arequest message to the device, and the request message may include apreamble or other predefined data fields. The device (e.g., a TS such asa CMTS) may analyze the data fields to determine the quality of thereceived signal as well as to determine the adjustment the user terminalshould make to its equalization coefficients to compensate fordistortion. The device may send a response message with equalizationcoefficients to be used by the user terminal In some embodiments, theresponse message may include a parameter or flag that directs the userterminal on how to interpret the equalization coefficients included inthe response message. For example, the parameter may instruct the userterminal to replace the equalization coefficients presently used by theuser terminal with the equalization coefficients included in theresponse message. Alternatively, the parameter may instruct the userterminal to combine (e.g., via a weighted summation, convolution, or thelike) the equalization coefficients presently used by the user terminalwith the equalization coefficients included in the response message.

While discussed above as a single request-response message set, in someembodiments a plurality of request-response messages may be exchangedbetween the user terminal and the device (e.g., a TS) before a final setof equalization coefficients is established for use by the user terminalAn exchange of multiple messages may have a tendency to average anydynamic characteristics associated with the communication channel'sfrequency response, thereby allowing the final set of equalizationcoefficients to approximate or settle on the typical channel frequencyresponse.

In terms of updating the equalization coefficients used by the userterminal, any number of techniques may be implemented as a function ofthe network's desired operation. For example, the request/responsemessage sequence described above may be periodically repeated (e.g.,every thirty seconds, every minute, etc.). Alternatively, the userterminal and the device may be arranged as a master-slave configuration,with one of the user terminal and the device initiating an equalizationcoefficient update. In some embodiments, the request-response messages(or more specifically, the functionality associated with therequest-response messages in regards to establishing and updating theequalization coefficients) may be incorporated in messages that are usedfor payload or data exchange between the user terminal and the device.

In terms of scheduling an update of the equalization coefficients, if auser terminal or a communication channel has demonstrated issues orproblems, the frequency of monitoring or updating the equalizationcoefficients may be increased relative to those terminals orcommunication channels that have not experienced any (or haveexperienced less) issues or problems. Also, if a particular terminal isdeemed to be of particular importance (e.g., a terminal that isresponsible for communicating data related to the transportation oftoxic chemicals), that terminal may be given priority in terms ofmonitoring and updating relative to other, less important terminals.

In some embodiments, (post-)equalization may also be performed at thereceiving device (e.g., the TS). In an HFC network, for example, giventhat the CMTS frequently communicates with a plurality of user terminals(e.g., cable modems), and that each user terminal typically has its ownassociated frequency response with respect to the CMTS, a decision maybe made to perform equalization at the user terminals (pre-equalization)in order to minimize the processing load on the CMTS. Sincepost-equalization operations start off every new data burst fromscratch, there is no memory condition to become corrupted from any givenerror condition. Also, in low frequency operating environments (e.g.,less than 20 MHz) where ingress and impulse noise are common,post-equalization may provide more stable performance. Post-equalizationmay also enable the user terminals to use lower transmit levels as thereis no requirement of a pre-equalization function being convolved at theuser terminal for post-equalization to work.

The equalization coefficients (or energy distribution information) maybe manipulated to determine an approximate distance of a source of apotential problem relative to the location of a transmitting device(e.g., a user terminal transmitting to a TS on an upstream channel).This enhanced resolution in terms of localizing the problem source mayserve to decrease debugging time and minimize downtime. Localizing theproblem source based on the coefficients will be described below inconjunction with FIGS. 5A and 5B.

FIGS. 5A-5B illustrate bar graphs similar to the one shown in FIG. 4. InFIG. 5A, there are large energy peaks repeated every three samplingperiods starting with tap 8 and progressing to the right (e.g., the barsassociated with taps 8, 11, 14, 17, 20, and 23 are large relative to thebars associated with taps 9, 10, 12, 13, 15, 16, 18, 19, 21, 22, and24). Assuming a symbol sampling frequency of 5.12 Mega symbols persecond (Msps) (and a corresponding sampling period of 195 ns), the timeperiod between errors is equal to 3×195 ns=585 ns.

The time period between errors may be manipulated to determine adistance between errors using velocity of propagation mathematics.Electromagnetic waves travel in free space at a known rate of983,571,056 feet per second (ft/sec). For example, assuming that thecommunication channel that was responsible for generating the bar graphof FIG. 5A is a coaxial cable in an HFC system characterized by avelocity of propagation (VoP) equal to 87% of the velocity ofpropagation associated with free space, then the velocity of propagationin the coaxial cable would be equal to 0.87×983,571,056ft/sec=855,706,819 ft/sec. Thus, given this velocity of propagation inthe coaxial cable, and the fact that velocity is equivalent to distancedivided by time, multiplying the velocity with the time between errorsyields the distance between errors: 855,706,819 ft/sec*585 ns=500 ft.Given that the source of the error caused the (error) signal to traversethe coaxial cable twice (once as a result of the signal beingtransmitted from the transmitter of the user terminal to the location ofthe error source, and a second time as a result of an echo or reflectionback from the error source to the transmitter), dividing the calculateddistance by two yields: 500 ft/2=250 ft. This type of analysis isapplicable to other communication media.

Thus, one could conclude that the source of the error is locatedapproximately 250 ft from the user terminal in this example. Given thatmost user locations (e.g., homes 102 of FIGS. 1 and 2) include somewherebetween 150 ft and 175 ft of signal transmission lines, in thisillustrative scenario it is likely that the source of the error islocated outside of the user's premises.

The example discussed above in connection with FIG. 5A (and morespecifically, the numerical values used) is merely illustrative. Thevalues used in the calculations may be modified in some embodiments, anddifferent bar graphs or equalization coefficients may be obtained invarious embodiments. For example, the approximate index of refractionfor a single mode optical fiber at 1310 nm is 1.46, making its velocityof propagation 68% that of free space. Assuming that the bar graph ofFIG. 5A was generated for a fiber optic implementation, the calculationsdescribed above in connection with the coaxial cable could be repeatedfor the optical fiber, replacing the 87% velocity of propagation factorcharacteristic of the coaxial cable with the 68% velocity of propagationfactor characteristic of the optical fiber. A different value for theerror distance would be arrived at, given the different velocitycharacteristics between the two transmission media. In those embodimentswhere more than one type of transmission media is used (e.g., a hybridfiber-coax implementation), the calculations may encompass one or moreof the velocity of propagation parameters.

FIG. 5A represents a simplified (and what is likely to be a rare)scenario where the majority of the energy of the taps is distributed ata multiple of the (195 ns) sampling period. FIG. 5B illustrates another(and perhaps more common) scenario, where the energy is distributed moreuniformly across the taps in the presence of an error condition. Thecircles shown in FIG. 5B represent the tap spacing or T-spacing between(approximate) successive energy peaks. Averaging the spacing betweenpeaks yields: 3T+2T+2T+3T+3T/5=2.6T. Accordingly, the techniquesdescribed above in connection with the scenario in FIG. 5A (where theerror source was located at a distance corresponding to a multiple ofthe sampling period) can be generalized such that the location of theerror source can be determined anywhere in the communication channel. Asdemonstrated in FIG. 5B, the tap energy represents a single echo howeverthe first incident energy is distributed between taps 10 and 11 with abias towards tap 11. In the case of a single echo, the subsequent peakstap spans are averaged to obtain a finer granularity (resolutioncorresponding to values less than T). For example, when modeling using2T-3T at 0.1T intervals, the averaging narrows the approximation to0.25T accuracy.

To this point, the discussion in relation to FIGS. 5A and 5B has beenbased on determining the location of a single error. Of course, in someinstances the communication channel may be subjected to multiple errorsor error sources. In general, multiple errors may cause waveforms to addconstructively, destructively, or cancel one another out completely(thus appearing as if no error is present). A few general points can bemade regarding the presence of multiple errors. An analysis of multipleuser terminals demonstrating a similar or common error/failure conditionis likely indicative of a plant error as opposed to an error inside auser's premises. Reflections in the plant generally tend to be lower insize. Maintenance of accurate plant mappings can help to isolateproblems. In general, large distortions are typical of in-home or userlocation wiring issues which most of the time consist of a single pairof reflectors. Feedback from field studies suggests that user locationwiring issues are the source of approximately 85% of the issues/errorsencountered, although any given typology or environment may beassociated with any number of issues/errors at any given location.

FIG. 6 illustrates a method that may be used in connection with one ormore aspects of this disclosure. The method illustrated in FIG. 6 isfrom the perspective of a receiving device, such as a termination system(TS). The steps may be modified so as to be viewed from the perspectiveof a user terminal or any other device. One or more steps of FIG. 6 mayperform a variety of functions including transforming an article (e.g.,equalization coefficients in conjunction with a received signal) into adifferent state or thing (e.g., a likely or approximate location of asource of a problem or error).

In step 604, the TS may receive a request message from the user terminalThe request message may include a preamble or other predefined datafields, and optionally, payload or application related data. The requestmessage may be processed by the TS to determine the qualities of thesignal associated with the request message. Based on the qualities ofthe signal, the TS may establish or generate a set of equalizationcoefficients to be used by the user terminal

In step 610, the TS may transmit a response message to the userterminal. The response message may include the equalization coefficientsthat were established for use by the user terminal The response messagemay also include a parameter or flag directing the user terminal how tointerpret or use equalization coefficients included in the responsemessage. For example, as described above, the parameter may indicatewhether the user terminal should replace the set of equalizationcoefficients currently used by the user terminal with the coefficientsincluded in the response message, or whether the user terminal shouldcombine (e.g., convolve) the set of equalization coefficients currentlyused by the user terminal with the coefficients included in the responsemessage. The response message may include any other data needed by theuser terminal to facilitate communication with the TS or another device.

As discussed above, the user terminal and TS may engage in a series orsequence of request-response message communications to obtain a stableor average set of values for the equalization coefficients. In thisrespect, steps 604 and 610 may repeat a number of times (e.g., as partof a looping operation) in some embodiments (not shown in FIG. 6).

In step 616, the equalization coefficients used by the user terminal maybe retrieved. For example, the TS may poll the user terminal in order toobtain perspective on the state (e.g., the frequency response) of thecommunications between the TS and the user terminal Alternatively, insome embodiments, the TS may store a copy of the equalizationcoefficients used by the user terminal and step 616 may include the TSretrieving those coefficients from memory associated with the TS.Periodically retrieving the coefficients and conducting an analysis asdescribed below may facilitate proactive network management byuncovering potential problems before they manifest themselves asfailures at the user terminal Retrieving and conducting an analysis inthe manner described may also be used as a reactive measure in responseto a reported failure.

In some embodiments, retrieving the coefficients may entail obtainingthe coefficients from both of the user terminal and the TS (e.g., from amemory associated with the TS). Using this latter technique, thecoefficients obtained from the user terminal can be compared with thecoefficients stored in the memory associated with the TS to determinewhether the coefficients match. If the coefficients do not match (withina threshold), such a condition may be indicative of a hardware orsoftware failure at one or both of the user terminal and the TS. Acomparison could also be made between the TS and one or more other userterminals to try and isolate the problem (e.g., to determine whether thecoefficient mismatch is likely due to a failing TS or whether thecoefficient mismatch is unique to a particular user terminal). In someembodiments, one or more additional devices (e.g., a handheld mobilestation) may be used to retrieve coefficients from the TS and/or userterminal in order to take the communication channel between the TS andthe user terminal out of the equation.

In some embodiments, the convolution process may occur in twoplaces/times—(1) during station maintenance and (2) duringburst-receive. A TS may be configured to perform station maintenanceusing low-order QAM (QPSK) regardless of the modulation profile (64QAM,etc). Having a preamble using a robust modulation allows equalization toconvolve around problems that might otherwise be too extreme and breakthe high-order QAM conversation. In a production plant, equalization notonly works but it works so well that without it many (e.g., 64QAM)channels would have poor performance (if the channels would be operativeat all).

In step 622, the signal received from the user terminal may be analyzedby the TS in conjunction with the coefficients retrieved via step 616.The analysis may include generating a displayable tap bar graph similarto the ones shown in FIGS. 4 and 5A-5B. The analysis may also includedetermining an approximate location of a problem or error source. Forexample, as discussed above, velocity of propagation mathematics may beused to determine the likely location of a source of a problem or error.

In step 628, a status message may be generated by the TS based on theanalysis conducted in step 622. The status message may indicate thedistance from the user terminal (or TS) to the source of the problem.The status message may include additional information that may be usedto facilitate debugging or troubleshooting. For example, the TS maymaintain a library or database of past issues or problems (with possibleinput from service personnel or the like) and the causes of those pastproblems. In this manner, the library or database may be consulted toidentify not only the likely location of the problem or error, but thelikely cause of the problem or error. Having such knowledge in advanceof going to the site of the problem may enable service personnel to packappropriate tool sets and may facilitate the selection of servicepersonnel (e.g., if correcting the problem entails a specific skill set,one service technician could be selected over another).

The status message generated in step 628 may be conveyed in one or moreformats. For example, the status message may include an audio message(e.g., a broadcast over radio), an email, a text message, an image/videomessage, or the like. If the problem is located in the user's premises(e.g., the user's home), the status message may be conveyed to the userand may either ask the user to schedule an appointment with servicepersonnel, or if the problem is simple enough to correct (e.g., a looseconnector), may provide the user with guidance (e.g., an instructionalvideo) on how to fix the problem.

The method described above with respect to FIG. 6 is illustrative. Insome embodiments, some of the steps may be optional, additional stepsnot shown may be included, and the steps may be rearranged or reordered.For example, in some embodiments coefficients may be obtained frommultiple user terminals for purposes of isolating problems (ordetermining the likelihood of where a problem exists).

While the above description was presented largely in the context of userterminals in communication with a TS, aspects of this disclosure mayreadily be applied to other contexts as well. For example, the qualitiesof peer to peer communication systems, (mobile) telephone communicationsystems, satellite communication systems, and the like may also bemonitored and evaluated using the techniques described herein. Ofcourse, the contexts described herein are merely illustrative.Additional contexts are well within the scope and spirit of thisdisclosure.

Although not required, various aspects described herein may be embodiedas a method, a data processing system, or as a computer-readable mediumstoring executable instructions. Accordingly, those aspects may take theform of an entirely hardware embodiment, an entirely softwareembodiment, an entirely firmware embodiment, or an embodiment combiningsoftware, firmware and hardware aspects. The functionality may beresident in a single computing device, or may be distributed acrossmultiple computing devices/platforms, the multiple computingdevices/platforms optionally being connected to one another via one ormore networks. In addition, various signals representing data or eventsas described herein may be transferred between a source and adestination in the form of electromagnetic waves traveling throughsignal-conducting media such as metal wires, optical fibers, and/orwireless transmission media (e.g., air and/or space). In someembodiments, one or more transitory and/or non-transitory media mayinclude instructions that, when executed by one or more computers orapparatuses, cause the one or more computers or apparatuses to performthe methodological acts and processes described herein.

As described herein, the various methods and acts may be operativeacross one or more computing servers and one or more networks. Thefunctionality may be distributed in any manner, or may be located in asingle computing device (e.g., a service provider's server, a clientcomputer/user terminal, etc.). As discussed herein, timing and frequencyinformation related to communications between two or more devices may beobtained across various television, telephone, and computer networks,and both proactive and reactive support in the presence of potentialproblems or actual errors is provided for.

As described herein, the methodological acts and processes may be tiedto particular machines or apparatuses. For example, as described herein,a user terminal, such as a cable modem, may equalize a signal prior totransmitting the signal to a receiving device (e.g., a TS). Thereceiving device may analyze the received signal in connection with theequalization coefficients to determine a likely location of a problem orerror. More generally, one or more computers may include one or moreprocessors and memory storing instructions, that when executed, performthe methodological acts and processes described herein. Furthermore, themethodological acts and processes described herein may perform a varietyof functions including transforming an article (e.g., equalizationcoefficients in conjunction with a received signal) into a differentstate or thing (e.g., a likely or approximate location of a source of aproblem or error).

The various embodiments and examples described above are, as stated,merely examples. Many variations may be implemented to suit a particularimplementation, and the various features may be combined, divided,rearranged, omitted and/or augmented as desired. The scope of thispatent should not be limited by any of the specific examples describedherein.

What is claimed is:
 1. A method comprising: retrieving a set ofequalization coefficients; determining an average value of time betweenpeak values in the set of equalization coefficients, wherein determiningof the average value of time comprises averaging a number of samplingperiods between peak values in the set of equalization coefficients;determining a velocity of propagation associated with a communicationchannel associated with a user terminal; and determining a location ofan error source relative to a location of the user terminal based on theaverage value of time between peak values in the set of equalizationcoefficients and the velocity of propagation.
 2. The method of claim 1,further comprising: transmitting a second set of equalizationcoefficients and a parameter to the user terminal, wherein the parameteris configured to indicate to the user terminal how to interpret thesecond set of equalization coefficients.
 3. The method of claim 2,wherein the parameter is configured to indicate to the user terminalthat the user terminal is to replace the set of equalizationcoefficients with the second set of equalization coefficients.
 4. Themethod of claim 2, wherein the parameter is configured to indicate tothe user terminal that the user terminal is to combine the set ofequalization coefficients with the second set of equalizationcoefficients.
 5. The method of claim 1, further comprising: receiving arequest message from the user terminal, the request message including atleast one predefined data field; calculating a frequency responseassociated with the communication channel associated with the userterminal based on the at least one predefined data field; assigningvalues to the set of equalization coefficients based on the calculatedfrequency response; and transmitting the values assigned to the set ofequalization coefficients to the user terminal.
 6. The method of claim5, wherein the values assigned to the set of equalization coefficientscorrespond to the inverse of the calculated frequency response.
 7. Themethod of claim 1, wherein determining the velocity of propagationassociated with the user terminal comprises determining a percentage ofvelocity of propagation of the communication channel relative to avelocity of propagation of free space.
 8. The method of claim 1, whereinthe set of equalization coefficients includes at least one of: exactlytwelve (12) coefficients, exactly twenty-four (24) coefficients, andexactly thirty-six (36) coefficients.
 9. The method of claim 1, furthercomprising: generating a status message indicating the determinedlocation of the error source.
 10. The method of claim 9, wherein thegenerated status message indicates a probable cause of an error.
 11. Themethod of claim 9, wherein the status message comprises at least one ofan audio message, an email, a text message, an image, and a video. 12.An apparatus comprising: at least one processor; and memory storinginstructions that, when executed by the at least one processor, causethe apparatus to: retrieve a set of equalization coefficients; determinean average value of time between peak values in the set of equalizationcoefficients, wherein determining the average value of time comprisesaveraging a number of sampling periods between peak values in the set ofequalization coefficients; determine a velocity of propagationassociated with a communication channel associated with a user terminal:and determine a location of an error source relative to a location ofthe user terminal based on the average value of time between peak valuesin the set of equalization coefficients and the velocity of propagation.13. The apparatus of claim 12, wherein the instructions, when executedby the at least one processor, cause the apparatus to receive the set ofequalization coefficients from the user terminal.
 14. The apparatus ofclaim 12, wherein the instructions, when executed by the at least oneprocessor, cause the apparatus to: generate a displayable tap bar graphshowing amplitudes associated with the set of equalization coefficientsas a function of a sampling period.
 15. One or more non-transitorycomputer-readable media storing executable instructions that, whenexecuted by at least one computer, cause the at least one computer to:retrieve a set of equalization coefficients; determine an average valueof time between peak values in the set of equalization coefficients,wherein determining the average value of time comprises averaging anumber of sampling periods between peak values in the set ofequalization coefficients; determine a velocity of propagationassociated with a communication channel associated with a user terminal;and determine a location of an error source relative to a location ofthe device based on the average time between peak values in the set ofequalization coefficients and the velocity of propagation.
 16. The oneor more non-transitory computer-readable media of claim 15, wherein theexecutable instructions, when executed by at least one computer, furthercause the at least one computer to: generate a status message indicatingthe determined location of the error source.
 17. The one or morenon-transitory computer-readable media of claim 16, wherein thegenerated status message indicates a probable cause of an error.
 18. Theapparatus of claim 12, wherein the instructions, when executed by the atleast one processor, cause the apparatus to: generate a status messageindicating the determined location of the error source.
 19. Theapparatus of claim 18, wherein the generated status message indicates aprobable cause of an error.
 20. The method of claim 18, wherein thestatus message comprises at least one of an audio message, an email, atext message, an image, and a video.